The present invention relates to a semiconductor device. The present invention also relates to a video display system having the semiconductor device and a method of outputting a video signal.
Patent Reference 1 has disclosed a conventional video display system for selecting and displaying a video among a plurality of videos. According to Patent Reference 1, when the conventional video display system is instructed to switch a video signal to a television video signal while the conventional video display system displays a navigation video, the navigation video is first switched to a pink image. As a result, a color determining portion of the conventional video display system generates a chroma key signal. Accordingly, the conventional video display system switches the video signal to the television video signal.
Patent Reference 1: Japanese Patent Publication No. 2008-99254
Patent Reference 2 has disclosed another conventional video display system. According to Patent Reference 2, when the conventional video display system is started, a display controller performs setting according to setting data stored in a memory, so that a selector selects a video signal directly supplied from a backup camera. Then, the conventional video display system converts a resolution of the video signal and supplies the video signal to an LCD (Liquid Crystal Display) panel. After a system controller is started, the selector selects the video signal supplied from the system controller, so that the video signal is supplied to the LCD panel.
Patent Reference 2: Japanese Patent Publication No. 2013-7907
As described above, in order for the conventional video display system to select and display one of a plurality of videos, the selector is provided for selecting and outputting the video signal from a plurality of video signals input thereto. More specifically, the selector of the conventional video display system is configured to perform such a simple operation as instantly switching the video signal from a plurality of video signals input externally. Accordingly, the selector of the conventional video display system is configured to output the video signal selected not in synchronization with a vertical synchronization signal.
In the conventional video display systems described above, when the video signal selected with the selector while not being in synchronization with the vertical synchronization signal is input into the LCD panel, the video to be displayed tends to be distorted until the video signal is synchronized with the vertical synchronization signal after the video signal is switched. In order to prevent the video to be displayed from being distorted, the conventional video display systems may be configured to perform video muting. However, if the conventional video display systems perform the video muting every time the video is switched, a work load of the conventional video display systems tends to increase.
In view of the problems of the conventional video display system described above, an object of the present invention is to provide a semiconductor device, a video display system, and a method of outputting a video signal capable of preventing a video to be displayed from being distorted when the video is switched.
Further objects and advantages of the invention will be apparent from the following description of the invention.